A purged argon pre-chamber for analytical glow discharge—time of flight mass spectrometry applications

Abstract

Aiming at minimizing microleaks in the seal between the sample and the GD, a surrounding chamber which warrants a continuous isolating argon flow around the solid sample during the analysis, has been investigated for radiofrequency (rf) glow discharge (GD) coupled to time of flight mass spectrometry (TOFMS) applications. Three standard reference materials and two thin coatings were analysed comparing the influence of the purging pre-chamber in the analytical results, both in non-pulsed and pulsed rf-GD operation modes. Results show that the external argon flow seems to reduce the microleaks between the sample and the GD source since a diminished level of polyatomics appeared in the recorded mass spectra. Additionally, using the rf non-pulsed mode better signal reproducibility, less polyatomic interferences and, in some cases, higher ion signals could be achieved. In terms of in-depth profile capabilities, a faster penetration rate was observed when the pre-chamber was used and such difference was dependent on the sample composition. Comparatively, less benefit was apparent using the rf-pulsed mode as the temporal discrimination in such mode allows to separate analytical ion signals from interfering contaminants.